La Marzocco GS3 - Excessive Water Consumption

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#1: Post by Zachary »

This is a GS3 AV and it's roughly 6 years old. LM tech came to service it 6 months ago for the first time. I believe he worked on the safety valve and vacuum valve? He said it was in great condition, we have extremely soft water. After the service it was moved to a different residence far away from any LM tech, hence the post, and last month it really started drinking water. Since the move, only thing that's changed is the water being used which is TWW espresso blend. It's not plumbed in and the pump goes on far more often than before and as a result the tank needs to be filled far more often.

Any tips would be much appreciated.

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#2: Post by Peppersass »

Looks like steam is leaking from either the steam boiler over-pressure valve (OPV), which you called the safety valve, or the steam boiler vacuum breaker. A steam leak will reduce the water level in the steam boiler and the pump will kick on, using up water in the reservoir.

To determine which valve is leaking, remove the right side cover and trace the plastic tube from the fitting above the drain box that's venting steam and water back to the OPV or vacuum breaker.

If the OPV is venting, the first thing to check is the steam boiler pressure. It should not be over 2 BAR. The OPV will open at 3 BAR. If your steam boiler pressure is above 2 BAR, reduce the steam boiler target temperature. If that doesn't lower the pressure, something is wrong with the steam boiler temperature probe or heating circuit. Don't use the machine until that's fixed.

If the OPV is venting, but the steam boiler pressure is 2 BAR or less, then either the OPV was installed incorrectly or it's defective. I'd bet on improper installation, seeing as how it was serviced 6 months ago. It's possible the tech didn't tighten the bottom fitting enough, omitted the copper washer, reused the old washer or damaged the new washer. You can try tightening the fitting on the bottom. I believe you'll have to disconnect the other end of the tube from the steam boiler in order to pull the can out of the machine to tighten the bottom fitting. You'll also need to remove the top of the can so you can hold the OPV with a wrench while you tighten the fitting. If it turns out the OPV is installed correctly, it's possible you have a defective OPV.

If the vacuum breaker is leaking, either it wasn't installed correctly or it needs to be serviced. If you got by for 6 years without the vacuum breaker needing service, your water must really be soft. It seems odd that it would fail only 6 months after servicing. That makes me wonder if the service tech didn't install it correctly. For example, if it's mounted at an angle the valve won't close properly. Might be a good ideal to take a photo and post it here.

If the valve has been installed correctly, then it needs to be serviced. Maybe a piece of debris got lodged in the valve when the machine was moved. Servicing isn't terribly difficult as long as you have the right tools. It's likely you have the previous-generation vacuum breaker, which is mounted on an L-connector on the top right side of the boiler. The valve has to be removed, disassembled and cleaned if necessary. Inside are a metal plunger, Teflon valve seat and an O-ring. Usually just the O-ring needs to be replaced. Sometimes it'll be worn out, sometimes it'll be caked with minerals. A very light coat of lubricant on the new O-ring before installation helps to extend service life. There are quite a few posts on servicing the GS/3 vacuum breaker here on HB. [Note: recently LM replaced the vacuum breaker with a thermostatically-activated model that supposedly has a much longer service life. It's black, rather than brass colored, and doesn't mount on an L-connector.]

Zachary (original poster)

#3: Post by Zachary (original poster) »

Thank you very much for the thorough and comprehensive response, it is very much appreciated.

I haven't been at the house since I made the post and the machine hasn't been used but I what I do know is that the steam is not over 2bar, so that can be eliminated (or my gauge is broken :lol: ) I'm going to buy some replacement parts before I head out there next. I believe the new vacuum breaker is B.2.029? Not entirely sure what the OPV is, potentially L190? And the copper washer I'm fairly certain is L100/1.

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#4: Post by AssafL »

Just another thought - since the water was changed maybe the new water has lower conductivity.

In the "Off" settings menu there is a setting for sensitivity that compensates for the lower conductivity and setting that to "high" may help.
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